This invention relates to a bag-making apparatus for forming a bag while the bag material travels continuously.
A conventional bag-making apparatus is shown in FIGS. 9 to 11. The bag-making apparatus 40 comprises a pair of forming rollers 41 which are arranged so as to contact the upper surface of the bag material 44, a dedicated forming plate 42 meeting the bag width of the tubular bag material, pressing rollers 43 disposed on the forming plate 42 with prescribed intervals, guide plates 45 arranged in the traveling direction of the bag material 44 together with the pressing rollers 43 and conveying rollers 46. The forming rollers 41 movable in the cross direction of the bag material 44 move according to the bag width, and crease lines at a distance corresponding to the bag width. The forming plate 42 contact the upper surface of the bag material 44, and both sides of the bag material 44 are folded. Thus, the bag material 44 is lapped around the forming plate 42, and made tubular. The pressing rollers 43 press both side edges of the folded bag material upon the forming plate 42. The guide plates 45 guide the bag material 44 before and after pressing by the pressing rollers 43. The conveying rollers 46 convey the bag material which has been formed tubular.
When the bag material was made tubular using the above apparatus 40, first, the upper surface of the bag material 44 was pressed by the forming roller 41, and both side portions were folded upward obliquely. Then, the forming plate 42 was applied along the crease line folded by the forming rollers 41, and both folded side portions were guided by the guide plates 45 so that they came near together in a state that the bottom and both side edges of the forming plate 42 contacted the bag material 44. The both folded side portions were pressed downwardly by the pressing rollers 43 to form the bag material tubular around the forming plate 42. When the bag width was changed, the traveling of the bag material was stopped. Then, the guide plates 45, the pressing rollers 43 and conveying rollers 46 were transferred to the outside of the apparatus temporarily, and the forming rollers 41 were moved in the cross direction so that they had a distance corresponding to the bag width. Subsequently, the tubular bag material surrounding the forming plate 42 was opened or removed, and the forming plate 42 was changed for another dedicated forming plate corresponding to the prescribed bag width. Then, the bag material was lapped around the new forming plate, and the guide plates 45 and the pressing rollers 43 were adjusted with regard to their positions in the traveling direction of the bag material, pressing force, etc., with conveying the bag material and making it tubular.
A conventional bag-making apparatus for making gusset bag is shown in FIGS. 12 to 14. The bag-making apparatus 47 comprises a forming plate 49 of which the approach side is bent to form an inclined face, guide bars 50 disposed on both sides in the cross direction of the forming plate 49, pressing rollers 51 disposed on the forming plate 49 in the traveling direction of the bag material 48, creasing rollers 52 disposed on both sides of the forming plate 49 perpendicular to the pressing rollers 51, and nip rolls 53 for nipping the bag material 48 formed tubular. The forming plate 49 is composed of two plates 49a, 49a disposed horizontally in parallel and a Joining member 49b Joining them at the central part. The forming plate 49 is used for making the bag material tubular by lapping the bag material around it, and has a dedicated size for each gusset bag. The guide bars 50 fold the bag material 48 so as to lap the forming plate 49, and are formed in L-shape. The pressing rollers 51 press the bag material formed tubular on the forming plate 49. The creasing rollers 52 form a crease by pressing on the central portion of each side of the bag material 48 formed tubular by the forming plate 49 and the guide bars 50.
When the bag material was made tubular using the above apparatus 47, both side portions of the bag material 48 were folded upward by the guide bars 50 in a state that the upper surface of the bag material 48 contacted the bottom face of the forming plate 49. The folded portions were pressed by the pressing roller 51 to form the bag material 48 tubular, while the creasing rollers 52 were pressed on the central portion of each side of the bag material 48 to form gusset. Thereafter, the bag material was pressed by the nip rollers 53, and a gusset type tube was completed. When the bag width was changed, the traveling of the bag material was stopped. Then, the guide bars 53, the pressing rollers 51 and the creasing rollers 52 were transferred to the outside of the apparatus temporarily, and the tubular bag material was opened or removed. The forming pate 49 was changed for another dedicated forming plate corresponding to the prescribed bag width. Then, the bag material 48 was lapped around the new forming plate, and the guide bars 50, the pressing rollers 51 and the creasing rollers 52 were returned to the prescribed position. The traveling of the bag material 48 was resumed, and the guide bars 50, the pressing rollers 51 and the creasing rollers 52 were adjusted with regard to their positions, pressing force, etc. with confirming the state of the tubular bag material (Japanese Patent KOKAI No. 55-103946).
As mentioned above, in the case of the conventional bag-making apparatuses, when the bag width was changed, the traveling of the bag material must be once stopped, and then, the forming plate was changed for another dedicated forming plate corresponding to the prescribed bag width. As a result, the working time was increased, and the productive efficiency was lowered. In order to change the forming plate, the tubular bag material surrounding the forming plate must be opened or removed also resulting to increase the working time and to lower the productive efficiency. After the forming plate was changed, the traveling of the bag material must be resumed in the state that the guide plates or bars, the pressing rollers, etc. were temporarily positioned. The optimum positions of them must be determined by adjusting the conditions with confirming the state of the tubular bag material, such as its size. Therefore, a considerable time was necessary until the optimum positions were determined resulting that the state of the tubular bag material became good. As a result, the productive efficiency was lowered due to the increase of the loss of the bag material, as well as the working time was increased.